Conduit for circulation of fluid under pressure

ABSTRACT

The invention relates to a conduit for circulation of fluid comprising a sealed pipe (A) fixed to a rigid supporting body (B) comprising a horizontal base having a lower face bearing on a laying surface (C) and two lateral wings going up vertically along the sites of the lower section of the pipe (A), said supporting body (B) comprising, on either side of the tubular enclosure (A), a single-piece portion ( 31, 31′ ) having, as a transversal section, a L-shaped profile comprising a substantially vertical branch ( 32 ) forming the wing extending along the corresponding side of the enclosure (A) and a substantially horizontal branch ( 33 ) extending beneath the former in order to form at least a portion of the base ( 3 ) of the supporting body (B) resting on the ground (C).

[0001] This application is a continuation in part application of serialNo. 08/765,422 of Jun. 28, 1995

FIELD OF THE INVENTION

[0002] This invention relates to a fluid circulation conduit, of verylarge transversal section, liable to exceed 2 m², which can be buriedunder an embankment and more particularly intended for the circulationof fluid under high pressure, in the order of several bars.

BACKGROUND OF THE INVENTION

[0003] A fluid transportation conduit can be made simply in the form ofmetal or concrete pipe elements, butt jointed and whose ends areinserted into one another, with interposed joints. In case of sinking,some elements may come loose and therefore, to resist relatively highpressures, it is preferable to use metal pipes whose elements are weldedat their adjacent ends, for instance, in the case of forced conduit forhydro-electrical plants.

[0004] In such a case, the conduit is composed of prefabricated pipeelements or of curved panels, which are transported to the site andwelded there. At that moment, however, the pipe is not under pressureand may deform while taking an oval shape, which makes welding moredifficult since the sheets would not be aligned any longer.

[0005] Besides, such pipes must often be buried, for instance in thecase of pipelines or gas-lines. When the pipe is under pressure, it caneasily sustain the loads applied externally by the embankment. But thepressure may vary and even become negative with respect to the outside.There is then a high risk of deformation of the pipe.

[0006] For all these reasons, the pipes performed by welding metalelements exhibit relatively limited section, most often smaller than 2m².

[0007] The inventor has been studying for several years a new techniqueto produce conduits for the transportation of fluid under pressure whichdo not exhibit such shortcomings.

[0008] With such a technique, the conduit is composed of a sealedthin-walled pipe, normally a metal pipe, fastened to a rigid supportingbody, usually made of reinforced concrete or preloaded concrete. Thus,the metal pipe enables the system to be sealed and to resist theinternal pressure, whereas the thin wall is solely subjected to tractionstresses, whereas the concrete body makes the conduit rigid whilebearing upon the laying surface on a widened surface enabling todistribute the loads applied and to better resist differential sinking.

[0009] In the technique described in the U.S. patent application Ser.No. 08/765,422 of Jun. 28, 1995, the concrete supporting body consistsadvantageously of three sections, respectively a horizontal base bearingon the ground and two lateral bearing parts forming vertical legs alongeach side of the pipe, whereby the assembly exhibits a U-shaped profilesurrounding the whole lower section of the pipe. The said pipe thereforeconsists, as a straight section, of four panels, respectively a lowerpanel applied onto the base, two lateral panels applied respectivelyonto both lateral legs and an upper panel with two lateral edges whichconnect tangentially to the corresponding ends of two side panels. Thesaid side panels are held by both legs of the supporting body and theiropposite edges can be thus perfectly aligned for welding purposes.

[0010] Such a conduit can be easily made from prefabricated elementswhose length is compatible with the transportation and handlingcapacities.

[0011] The inventor went even further in his studies with a view tosimplifying the production technique of such a conduit, in particular tomake the various prefabricated elements lighter and to facilitate theirinstallation, while keeping the various advantages provided by the artso far.

SUMMARY OF THE INVENTION

[0012] The invention therefore relates generally to a fluid circulationconduit, of large transversal section, of the type in excess of 2 m²,comprising a pipe having a longitudinal axis and fixed on a rigidsupporting body bearing on a laying surface, said pipe forming a sealedtubular enclosure constituted of a plurality of juxtaposed panels of athin wall and comprising a lower part having a U-shaped profile with twosides and an upper part, said supporting body comprising a horizontalbase with a lower plane face bearing on the laying surface and twolateral wings going up vertically along the sides of the lower part ofthe tubular enclosure, wherein the supporting body comprises, on eitherside of the tubular enclosure, a single-piece portion having, incross-section, an L-shaped profile comprising a substantially verticalbranch forming a lateral wing of the supporting body extending along thecorresponding side of the lower part of the pipe and a substantiallyhorizontal branch extending beneath the said lower part of the pipe andforming at least a portion of the base of the supporting body resting ofthe laying surface.

[0013] Particularly advantageously, at least over a certain length ofthe pipe, both lateral wings and the base of the supporting body form aU-shaped single piece.

[0014] According to another embodiment, at least over a certain lengthof the pipe, the supporting body comprises two L-shaped profile pieceswhose horizontal branches connect on either side of the medium plane ofthe pipe passing through the longitudinal axis, in order to form acontinuous base.

[0015] Normally, the supporting body is made of reinforced concrete andthe reinforcement can be made conventionally to sustain the loadsapplied, in particular, loads tending to spread the lateral sectionsapart. However, according to another particularly advantageous feature,the reinforcement may be made of at least one curved sheet, embedded inthe concrete supporting body and having two branches, respectivelyhorizontal and vertical, extending each into the corresponding branch ofeach L-shaped portion of the supporting body.

[0016] Preferably, to ensure transmission continuity of the loads, eachL-shaped lateral part of the supporting body comprises an internal facefor application and fixation of the enclosure, whose orientation variesgradually between a substantially horizontal lower section and asubstantially vertical upper section.

[0017] Other advantageous features are the subject matter of thesub-claims.

[0018] But the invention will be understood better by the followingdescription of certain embodiments given for exemplification purposesand represented on the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a schematic view, as a transversal and perspectivesection, of a portion of a conduit according to the invention.

[0020]FIG. 2 shows schematically the deformation conditions of aconduit, in case of depression with respect to the outside.

[0021]FIG. 3 shows an another embodiment.

[0022]FIG. 4 is a detailed view of the other embodiment of FIG. 3.

[0023]FIG. 5 is a transversal sectional view of another embodiment.

[0024]FIG. 6 shows schematically the execution and the transportation ofthe prefabricated elements.

[0025]FIG. 7 shows an another embodiment with an interconnectioncrossbeam.

[0026]FIGS. 8 and 9 illustrate embodiments enabling to change thedirection of the conduit axis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027]FIG. 1 is a schematic representation, in perspective, of a portionof a conduit according to the invention consisting, generally, of a pipeA associated with a concrete supporting body B. The pipe A consists ofcurved metal panels, welded along their adjacent edges, whereas thenumber of panels depends on the passage section to be provided. For apassage section of about 2 meters in width, the pipe A may comprise twopanels only, respectively a lower panel 1 constituting the lower part ofthe tubular enclosure and an upper panel 2 constituting the upper part,said panels 1, 2 being welded along their longitudinal adjacent edges11, 21, 11′, 21′. Each panel 1, 2 covers, in the direction of thelongitudinal axis O, O′ of the conduit, a length L depending on thetransportation possibilities. The panels 1 a, 1 b, 2 a; 2 b of twosuccessive sections of the pipe, are welded along their oppositetransversal edges 12 a, 12 b, 22 a, 22 b, in order to constitute asealed tubular enclosure A resisting an internal pressure.

[0028] The tubular enclosure A is applied onto a supporting body B whichsurrounds its whole lower section and therefore exhibits a U-shapecomprising a base 3 and two lateral wings 31, 31′ going up verticallyalong both lateral sides of the enclosure A. The assembly is symmetricalwith respect to a vertical medium plane P1 passing through thelongitudinal axis O, O′.

[0029] Both wings 31, 31′ of the base B extend up substantially to thelevel of the horizontal diametrical plane P2 of the pipe, passingthrough the axis O, O′ and, even, slightly above this plane in theembodiment represented on FIG. 1.

[0030] Both lateral sides 13, 13′ of the lower panel 1 of the enclosureA may still reach above the plane P2 since they are stiffened by bothwings 31, 31′ of the base and their longitudinal edges 11, 11′ aretherefore held parallel and aligned with the corresponding edges of theportion of the conduit already provided, which facilitates theinstallation and the welding of the upper panel 2. The lower panel 1then covers an angular sector greater than 180°, with a re-entrantangle, whereas the upper panel 2 covers the complementary angularsector.

[0031] The upper part of the pipe 1 made of the upper panel 2 and of thesides 13, 13′ of the lower panel 1, which connect tangentially, exhibitsadvantageously the shape of a sector of a cylinder of revolution centredon the axis O, O′, at least down to the diametrical plane P2. Thus, theenclosure A is able to resist the loads applied in best conditions.Indeed, the application of an internal pressure solely determines thetraction loads in the metal wall which is easily calculated and whosethickness may be relatively small. It should be noted that thesemi-circular shape of the wall 2, 13, 13′ enables the latter to resistin best conditions, not only an internal pressure but also externalloads, for instance, in the case of a conduit buried under an embankmentbefore pressurising the fluid inside the enclosure A.

[0032] The lower portion 1 does not to be semi-circular and may even beflat since the base 3 of the concrete supporting body B and thereinforcements thereof can be calculated in order to resist the bendingstresses.

[0033] In the embodiment described in the previous U.S. patentapplication Ser. No. 08/765,422 of the same inventor, the supportingbody consisted of three sections, respectively a base extending beneaththe lower section of the enclosure and two lateral bearing parts whichmaintain the sides of the enclosure and which are pushed against thelateral faces of the base by preloaded tie rods. Thus, the base issubjected to high compression stresses. Moreover, the junction betweenboth lateral bearing parts and the base of the supporting body works asan articulation.

[0034] In the present invention, conversely, the supporting body Bcomprises, on either side of the enclosure A, a lateral portionconsisting of a single-piece part 31 having, as a transversal section,an L-shaped profile which comprises a substantially vertical branch 32extending along the side corresponding to the enclosure A and asubstantially horizontal branch 33 extending beneath the pipe to form atleast a portion of the base 3 bearing on the ground, said L-shaped part31 having a curved inside face 38.

[0035] Such a layout enables to guarantee the transmission continuity ofthe loads, whereby the spreading stresses applied by the lateral sides13, 13′ of the enclosure A on both wings 32, 32′ of the supporting bodyB are absorbed by the base 3 of the said body.

[0036] Thus, the base is solely subjected to bending stresses resultingfrom the spreading tendency of the sides 32, 32′ which are, besides,compensated for by the weight of the pipe A and the application of thepressure onto its lower face 14.

[0037] The base 3 of the supporting body can then be made lighter and itis possible, even for very large sections, for instance, a diameter inthe order of 3 meters, to execute a single-piece supporting body such asrepresented on FIG. 1;

[0038] The supporting body B will, normally, consist of reinforcedconcrete, for instance as indicated as a partial section on FIG. 1. Thereinforcement 5 must then exhibit the desired U-shaped and may consist,conventionally, of longitudinal reinforcing steel rods 51 associatedwith transversal reinforcements 52.

[0039] The lower face 14 of the tubular enclosure may have a curvatureradius greater than that of the upper face 2 and can even be flat.However, the lower face 14, substantially horizontal, and the lateralsides 13, 13′, substantially vertical, of the panel 1, are appliedagainst the inside face 38 of the L-shaped part 31 of the body B and itis preferable to provide a gradual transition between the vertical 32and the horizontal 33 branches in order to guarantee transmissioncontinuity of the stresses without any angular point. Preferably, saidinside face 38 is continuously curved for having an orientation whichvaries gradually between a substantially horizontal lower section and asubstantially vertical section.

[0040] For exemplification purposes, FIG. 2 represents schematically, asa full line, a conduit according to the invention comprising a metalpipe A associated with a concrete base B and, as a mixed line, thedeform A′, B′, determined by calculation in the case of an excesspressure from the outside with respect to the inside of the conduit, forexample under the weight of an embankment.

[0041] Obviously, the scale of deformations has been amplified to makethem more visible but it can be seen that, thanks to continuoustransmission to the base 3, 33, 33′ of the spreading stresses applied tothe wings 32, 32′, of the concrete supporting body B, the latter deformsgradually, whereby both wings 32, 32′ maintain the rigidity of thetubular enclosure at the sides 13, 13′ of the said enclosure without anyrisk of breakage at the junction with the concrete supporting body B.

[0042] Thanks to the excellent distribution of the stresses over thewhole volume of the single-piece concrete supporting body B, the mass ofthe said body can be reduced considerably with respect to theembodiments known previously.

[0043] To make the structure still lighter, <<high performanceconcrete>> can advantageously be used, with compression and tractionresistance far greater than that of the ordinary concrete, for exampleabove 40 MPa. Such a resistance stimulates interconnection andco-operation between the metal pipe A and the concrete supporting bodyB. On the other hand, increasing the performances of the concreteenables to use high resistance steel. The thickness of the metal wallcan then be reduced and, consequently, the global weight of the elementsas well.

[0044] Moreover, as indicated on FIGS. 3 and 4, it is possible toimprove the junction between the metal wall A and the supporting body Busing angle iron 7, 7′, each forming at least one angle with a side 71covering the upper face 30′ of each wing 32, 32′ of the supporting bodyB and a side 72 extending upwards and tangent to the external face ofthe corresponding lateral side 13, 13′ of the thin wall A, at the outletof the supporting body B. The side 71 is sealed in the concrete and theside 72 is welded on the external face of the lateral side 13, 13′ whichis thus stiffened and held against the wing 32, 32′ of the supportingbody B, which enables to avoid any risk of separation liable to cause,for instance, water ingress.

[0045] The angle iron 7, 7′ is fitted with sealing parts 73 and mayadvantageously cover the external edge of the upper face 30′ of thesupporting body B to reduce the risks of concrete cracking.

[0046] Preferably, the angle iron 7, 7′ extend along the whole face 30′of the supporting body B, but they can also consist of simple sealingtabs, at a distance from one another.

[0047] According to another particularly advantageous feature,continuous transmission of the stresses in the supporting body B enablesto simplify the execution of the reinforcement, as represented on FIGS.3 and 4.

[0048] In such a case, indeed, the reinforcement can also consistessentially of a simple sheet 54 which is bent with the same curvatureas the wall 1 of the enclosure A and the inside face 38 of the body B,said sheet 54 being embedded in the concrete 30. Perforations 55provided over the whole surface of the sheet 54 guarantee thepenetration of the concrete for better interconnection. Moreover, asindicated on FIG. 4, the sheet 54 can also be provided, on both itsfaces, with protruding elements 56 for complete interconnection.

[0049] Both parallel sheets 1 and 54 connected by the concrete 30co-operate, together as a curved crossbeam in order to absorb thespreading stresses of the lateral sides 32, 32′.

[0050] To avoid cracking, it suffices to place in the angles of thesupporting body B, a light reinforcement 5′, for example a weldedwire-metting, in particular along the external faces of the supportingbody. However, according to another advantageous feature represented onFIG. 4, the concrete 30 can be a fibre concrete comprising, as alreadyknown, a plurality of metal fibres 57 distributed regularly in thesupporting body of the concrete and oriented randomly. Thus, theconcrete supporting body B can also be made lighter.

[0051] Thanks to the simplification of the reinforcement, as shown onFIG. 4, it is possible to provide, at each angle of the supporting body,a free space in which are placed pipes 58 butt jointed which can beinvolved in the resistance of the body B and delineate a longitudinalspace for the passage, for instance, of electric cables, of ducts or oflongitudinal preloaded bars.

[0052] The execution of the prefabricated elements and theirimplementation for the construction of a conduit according to theinvention are particularly simple, as shown schematically on FIG. 6.

[0053] The lower portion 1 of the tubular enclosure A may consist, evenfor great sizes, of sheet panels which are press-bent or roll-bent inorder to provide the requested curvature. To execute a prefabricatedelement of the conduit, the panel 1 is turned over and placed at thebottom of a mould 6 in order to constitute a disposable form. Asindicated on FIG. 4, the panel 1 has been provided in advance, on thetop side, with interconnection elements 53 such as welded profiles.After installing the lateral faces 61 of the mould and the reinforcement5, the panel 1 is placed and the concrete is cast up to the requestedlevel to provide the necessary thickness to the base B.

[0054] It should be noted that the sheet-shaped reinforcement of FIGS. 3and 4 could be fastened in advance, at the requested distance, on thepanel 1.

[0055] After setting, the assembly is removed from the mould and turnedover.

[0056] To handle the prefabricated element thus provided, the formermust obviously be provided with anchoring points such as rings 40 sealedin the concrete at the upper portion of the wings 32, 32′ and enablingslings to be hooked to the latter. If needed, the rings 40 can also bewelded to the angle iron 7 sealed on the upper face 30′ of thesupporting body B.

[0057] Such prefabricated elements can be transported easily to theconstruction site, for example on a trailer 62, as indicated on FIG. 6.It is thus possible to transport elements of very large sizes by road ifthe height h of the element, added that of the trailer, remainscompatible with the road gauge. Indeed, it suffices to delineate thelength L of the prefabricated element so that, the latter being placedtransversally on the trailer, the whole does not exceed the authorisedwidth.

[0058] The upper panels 2 of the pipe, consisting of bent sheets, can besimply stacked for their transportation to the site.

[0059] For the execution of the conduit, after having prepared theinstallation surface C, the prefabricated elements are placed one behindthe other along the longitudinal axis O, O′ while adjusting the levelsand the positioning so that the lateral edges 11 a, 11 b of the panels 1a, 1 b of the element B1 to be installed and of the element B alreadyinstalled, are placed in the alignment of one another, whereby thecorresponding transversal edges 12 a, 12 b contact each other.

[0060] The upper panel 2 a can then be installed and the assembly can bewelded along the joints, respectively longitudinal 11, 21 andtransversal 12, 22.

[0061] At each longitudinal end, the concrete supporting body B isstopped slightly recessed from the sheet 1 in order to leave between twoconsecutive elements B1, B2, a space 34 which makes the installation ofthe element and the welding of the sheets easier. The longitudinalreinforcement 51 are provided with standby portions that cross oneanother in this space 34 and are then embedded in a sealing mortar.

[0062] The execution of the conduit is therefore particularly easy,since the elements can be prefabricated in factory and then transportedto the building yard.

[0063] However, for very large sizes, it is also possible to execute theelements on site. The sheets 1, 2 can indeed be formed in the workshopand stacked on a trailer to be delivered to the yard, which only needsto be fitted with the necessary moulds 6, whereby the latter areparticularly simple. In the case of a large conduit, the element canthen be constructed close to the yard on mobile prefabrication units.

[0064] Obviously, if the supporting body B can be made lighter, it must,however, be calculated in relation to the circumstances of use. Forinstance, when the conduit is located inside the groundwater table, theconcrete supporting body advantageously operates as ballast and its massis therefore determined accordingly.

[0065] But the invention is obviously not limited to the details of theembodiments that have just been described, since other embodiments maybe contemplated without departing from the scope defined by the claims.

[0066] For instance, to make the supporting body still lighter, it wouldbe possible, as indicated on FIG. 3, to give a circular profile to thetubular enclosure A which resists then by itself the internal pressure,without applying any bending stresses onto the base 3 which providesessentially for the rigidity of the enclosure, in particular duringassembly, and serves to distribute the load over a great surface.However, the total height H of the element is increased and, for a largepassage section, the embodiment with flattened base of FIG. 1 will be,generally, preferable.

[0067] On the other hand, it is particularly advantageous to execute aU-shaped single-piece concrete supporting body, but it would bepossible, also, as represented on FIG. 5, to provide two L-shapedportions 36, 36′ having horizontal branches 33, 33′ which connect in themedium plane P1 of the conduit. The enclosure would then be constructedin order to leave between the opposite faces of both branches 33, 33′ afree space 37 in which standby reinforcements of both elements cross oneanother and co-operate with longitudinal reinforcements, whereby theassembly is embedded in a sealing mortar to provide the continuity ofthe base.

[0068] Besides, the level of the longitudinal joints 11, 21 can bevaried as well as the number of panels constituting the pipe A. However,the height (h′) of the lateral sides 32, 32′ must remain sufficient tomaintain the rigidity of the sides 13, 13′ and resist a crushing stressof the conduit when subjected to a depression with respect to theoutside.

[0069] Obviously, the concrete supporting body B must be relativelyresistant to enable handling, transportation and installation ofprefabricated elements. To make the supporting body B as light aspossible, it will be, sometimes, more interesting to strengthen it usinga linking crossbeam fixed on the upper ends of both wings 32, 32′ inorder to provide for the rigidity of the lower element during handlingoperations. This back-up crossbeam can be fastened removable, in orderto be removed after installation of the lower element, in order to mountthe upper panel 2. However, such a linking crossbeam can also exhibitadvantages after the construction of the conduit. Indeed, as indicatedon FIG. 7, it can be shaped as a cradle 41 of mechanical-weldedconstruction, spanning the conduit and exhibiting an inner profile 42identical to that of the upper wall 2. Such a cradle 41 can also befastened in advance to the upper panel 2 if the supporting body B issufficiently resistant for handling operations. The cradle 41 thenprovides for the external protection and reinforcement of the panel 2whose thickness can be reduced, whereas the said thickness can becalculated solely in relation to the traction loads caused by internalpressure. The panel 2 thus reinforced by one or several cradles 41, willbetter resist crushing when the conduit is depressurised with respect tothe outside.

[0070] A conduit according to the invention exhibits other advantagesstill.

[0071] For example, in curved portions of the conduit, the successiveconcrete elements can be linked to one another in order to prevent theconduit from slipping. As indicated on FIG. 8, the prefabricatedelements can easily be constructed so that the transversal jointing planQ in which are placed the transversal edges 12, 22 of the enclosure A istilted with respect to the longitudinal medium plane P1 of eachprefabricated element in order to enable, gradually, a change ofdirection. The successive elements can then be interconnected bypreloaded tie rods 43 which can advantageously be inserted into thetubes 58 described previously with reference to FIG. 4 and whose endsbear upon bosses 35 provided, externally, at the ends of each elementB1, B2.

[0072] In a similar way, as indicated on FIG. 9, the jointing plane Qcan be tilted with respect to the horizontal axis in order to suit anypitch variation of the laying surface C.

What is claimed is:
 1. A conduit for the circulation of fluid, of largetransversal section, of the type in excess of 2 m², comprising a pipehaving a longitudinal axis and fixed on a rigid supporting body bearingon a laying surface, a) said pipe forming a sealed tubular enclosureconstituted of a plurality of juxtaposed panels of a thin wall andcomprising a lower part having a u-shaped profile with two sides and anupper part, b) said supporting body comprising a horizontal base with alower plane face bearing on the laying surface and two lateral wingsgoing up vertically along the sides of the lower part of the tubularenclosure, c) wherein the supporting body comprises, on either side ofthe tubular enclosure, a single-piece portion having, in cross-section,an L-shaped profile comprising a substantially vertical branch forming alateral wing of the supporting body extending along the correspondingside of the lower part of the pipe and a substantially horizontal branchextending beneath the said lower part of the pipe and forming at least aportion of the base of the supporting body resting of the layingsurface.
 2. A conduit according to claim 1, wherein at least over acertain length, the supporting body is cast as a single piece, whereasthe horizontal branches of both L-shaped portions meet to form the baseof the supporting body.
 3. A conduit according to claim 1, wherein atleast over a certain length, the supporting body comprises of twoL-profiled portions with horizontal branches whose opposite ends areinterconnected in the medium plane of the enclosure passing through thelongitudinal axis in order to constitute a continuous base.
 4. A conduitaccording to claim 1, wherein the supporting body is made of reinforcedconcrete.
 5. A conduit according to claim 4, wherein at least in eachL-shaped portion, the supporting body is reinforced by a curved sheetembedded inside the concrete and having two branches, respectivelyhorizontal and vertical, each extending in the corresponding branch ofthe L-shaped portion of the supporting body.
 6. A conduit according toclaim 1, wherein each L-shaped section of the supporting body comprisesan internal face for application and fixation of the enclosure, whoseorientation varies gradually between a substantially horizontal lowersection and a substantially vertical upper section.
 7. A conduitaccording to claim 6, wherein the internal face of both branches of eachL-shaped section as well as the corresponding sections of the tubularenclosure have a curvature radius which varies continuously, without anyangular point.
 8. A conduit according to claim 1, wherein the supportingbody is made of reinforced fibre concrete.
 9. A conduit according toclaim 1, wherein each vertical branch of the supporting body is coveredat least partially with an angle iron forming at least one angle withone side sealed on the upper face of the branch of the supporting bodyand one side tangent to the lateral side of the enclosure, at the outletof the supporting body, and welded onto the latter.
 10. A conduitaccording to claim 1, wherein the supporting body is made of highperformance concrete, with compression resistance in excess of 40 MPa.11. A conduit according to claim 1, wherein the supporting body isprovided with a reinforcement composed of at least one curved sheetembedded in the concrete and substantially parallel to the lower sectionof the enclosure, the said sheet going up into the vertical branches ofthe supporting body.
 12. A conduit according to claim 1, wherein it isassociated with a number of spaced cradles distributed along the conduitand having an internal face surrounding the upper section of the tubularenclosure.
 13. A conduit according to claim 1, wherein it is composed ofprefabricated juxtaposed elements, each extending over a certain lengthof the conduit and each comprising a supporting body associated with atleast one sheet forming the lower portion of the enclosure and at leastone panel closing the upper portion of the enclosure and having twolateral sites welded on the longitudinal edges of the sheet.
 14. Aconduit according to claim 13, wherein at least two successive elementsare terminated, at their adjacent ends, by transversal jointing planestilted with respect to the axis of the pipe, in order to ensure a changeof direction of the axis of the conduit.